Miscellaneous Linux errors and the solutions

!!!!5. Silent davical failures after upgrading to Ubuntu 16.04 !!!Problem davical ceases to provide calendar data in response to PROPFIND requests from clients, returning only a 500 status. Debugging by instrumenting __/etc/davical/{conf}.php__ provides no further elucidation, but instrumenting __/usr/share/davical/CalDAVRequest.php__ shows executing aborting at this line: /// $xml_parser = xml_parser_create_ns('UTF-8'); /// !!!Cause Running __php -a__at the command line and executing the above line results in: /// PHP Warning: Uncaught Error: Call to undefined function xml_parser_create_ns /// !!!Cause Ubuntu 16.04 does not have a dependency link between the __davical__ package and the provider of the required function, __php7.0-xml__. Resolve with: /// sudo apt-get install php7.0-xml ///